Investigation the positive moments on the $M$$-$$T$ curve of YBCO films measured by using zero-field cooling
Guo Shu-Quan (郭树权)abc, Wang Feng-Lin (王凤林)a, Zhou Yue-Liang (周岳亮)b, Zhao Bai-Ru (赵柏儒)b, Gao Ju (高炬)c
a Applied Superconductivity Research Center, Department of Physics, Tsinghua University, Beijing 100084, China; b National Laboratory for Superconductivity, Institute of Physics, Chinese Academy Science, Beijing 100080, China; c Department of Physics, The University of Hong Kong, Hong Kong, China
Abstract The superconducting transition of a YBCO film was measured by a MPMS-5 superconducting quantum interference device magnetometer, using a zero-field cooling process. The experimental results have shown that there are positive magnetic moment and positive peak on the $M$$-$$T$ curve. We have proven that these anomalous behaviours are due to measurement error, but not phase transition. We have proposed a simple formula to explain and to calculate quantitatively these anomalous behaviours. It was found that, provided dH>0.59Hp (dH is the inhomogeneous field of the remnant field, Hp is the fully penetrated field of the measured sample), the experimental results will be positive, not negative. If dH≥2Hp, the experimental results will be symmetrical to their real negative values. From the $M$$-$$T$ curve, which has positive moment and positive peak below Tc (superconducting transition temperature), we found a new possible method to obtain Hp of the measured sample.
Received: 20 April 2001
Revised: 13 December 2001
Accepted manuscript online:
PACS:
74.78.-w
(Superconducting films and low-dimensional structures)
(Magnetic properties including vortex structures and related phenomena)
Fund: Project supported by the National High Technology Development Programme of China (Grant No 863-CD090000).
Cite this article:
Guo Shu-Quan (郭树权), Wang Feng-Lin (王凤林), Zhou Yue-Liang (周岳亮), Zhao Bai-Ru (赵柏儒), Gao Ju (高炬) Investigation the positive moments on the $M$$-$$T$ curve of YBCO films measured by using zero-field cooling 2002 Chinese Physics 11 379
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